It is a composite board made of resin soaked corrugated cardboard. It come with many different surface veneers, allows for simple joinery, can be kerf cut to make rounded corners. Wickedly strong, light weight, must have some insulation value due to the trapped air cells.
Dont know what kind of price they get for the stuff, waiting on a price list to come in. You can get free samples to check out, and I'm sure you'll be as impressed as I am! They also send tech info on joinery and other info that is sure to make you think WOW!
I can easily see taking down the ancient conversion materials that were put in in the '70s and replacing it with this stuff, and probably gain a slight amount of space since my walls will be much thinner.